This pre-clinical project will explore the unique biological attributes of muscle cells for their potential to act as gene therapy delivery vehicles for the continuous production of anti-neoplastic recombinant polypeptides in the treatment of malignancies. The overall hypothesis to be tested is that muscle cells can be engineered to secrete high levels of active polypeptides that can effect tumor growth and metastasis. Two forms of delivery will be evaluated: systemic delivery from cells implanted in skeletal muscle and local delivery from cells implanted at the sites of tumors. The effectiveness of myogenic cells will be compared with that of fibroblasts. Stable myogenic cell lines or primary myoblasts producing and secreting antineoplastic peptides in vitro will be created by transduction of expression vectors for several polypeptides including tissue inhibitors of metalloproteases (TIMPs) and somatostatin analogs (SSA) and, in collaboration with Project 4, cytokine genes. To insure muscle specific and high level expression, a series of combinations of muscle-specific enhancer and promoter elements will be evaluated in an efficient cell culture test system. The best performing promoter will he used for transduction of primary myoblasts and compared with expression from two standard promoters (CMV and beta-actin) and, in collaboration with Project 6, with a hypoxia responsive GRP78 promoter. Myogenic conversion of primary non-muscle cells, by the transduction or transfection of cDNAs expressing myogenic determination factors, may provide a readily available, expandable and renewable primary cell substrate for myoblast transfer gene therapy. The capacity of such cells to serve as constitutive secretors of recombinant polypeptides will also be tested. These experiments will attempt to determine the therapeutic effects in vivo of TIMPs and cytokine genes delivered locally by genetically engineered myoblasts in pre-tumor implantation models and established tumor growth models. The planned experiments will also determine the in vivo therapeutic efficacy against human breast cancer of systemically delivered SSA by transduced myoblasts in a pre-tumor implantation model, in an established tumor growth model and in a model of metastatic disease following the surgical removal of the primary tumor.